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Jan. 24, 1956 c. D. FISHER HAMMER MILL WITH SEPARATELY USABLE SCREENS 3 Sheets-Sheet 1 Filed March 24, 1953 20b 1 INVENTOR.

CHESTER D. FISHER ATTORNEYS Jan. 24, 1956 c, FlSHER 2,732,137

HAMMER MILL WITH SEPARATELY USABLE SCREENS Filed March 24, 1953 I 11 3 m1? FIG-4 zoa. f

3 Sheets-Sheet 2 IN V EN TOR.

CHESTER D. FISHER ATTORNEYS Jan. 24, 1956 c. D. FISHER HAMMER MILL WITH SEPARATELY USABLE SCREENS Filed March 24, 1955 3 Sheets-Sheet 3 FIG-9 W W W F U 0 UV 00 00 FIG-IO INVEN TOR. CHESTER D. FISHER United States Patent HAMMER MILL WITH SEPARATELY USABLE SCREENS Chester Donald Fisher, Muncy, Pa., assignor to Sprout,

Waldron and Company, Inc., Muncy, Pa., :1 corporation of Pennsylvania Application March 24, 1953, Serial No. 344,380

Claims. (Cl. 241-89) This invention relates to hammer mills, and more particularly to a hammer mill having provision for quick and easy variation of the degree of fineness of the ground product.

The invention has special relation to hammer mills of the type wherein the grinding operation is carried out by multiple swinging hammers rotating at relatively high speed to disintegrate the grain or other product to be ground as it enters the path of the hammers. The degree of fineness to which the product is ground is determined by the mesh of a screen which controls the discharge outlet from the mill. Thus particles which are insufficiently small to pass through a screen of the desired mesh are caused to return into the path of the hammers, as by bafiles or the like, for further disintegration, and at the same time additional unground product is fed into the mill until grinding of the entire batch has been completed.

It has been found in practice that there is commonly a wide range of grinding requirements for the same hammer mill, especially for uses such as the custom grinding of agricultural feeds where the majority of the customers appear to desire different degrees of fineness in their ground products. Such variation of the fineness of grinding is obtained by utilizing screens of different mesh which must be changed as required for each grinding operation in accordance with the particular properties desired in the ground product. If the mill is of the type wherein changing of the screen must be effected from within the housing, certain difiiculties are presented. For reasons of safety, the mill must be entirely stopped before the housing is opened for manual removal of the screen, and in view of the high speed operation of the mill and the resulting substantial momentum, it may take as much as several minutes after the power is shut off before the mill stops and it is safe to open the housing. Then after the screen has been removed and replaced, which is in itself a laborious operation, there is a further substantial time loss while the mill is again brought up to speed, which represents unproductive use of power in addition to. the loss of productive time.

It is accordingly one of the principal objects of the present invention to provide a hammer mill in which variation of the degree of fineness of the ground product may be quickly and easily obtained by changing the screen without stopping operation of the mill and with minimum manual effort on the part of the operator.

An additional object is to provide a hammer mill in which a plurality of separately usable individual screens are carried for selective use by a shiftable support mounted adjacent the main mill housing and in which the selected screen can be quickly and easily exchanged for the screen presently in use without interrupting operation of the mill and without requiring manual handling of either screen.

It is also an object of the invention to provide a hammer mill wherein the selected screen is located in the optimum position in the mill for eflicient operation and wherein also damage to an individual screen in use, as through puncture by foreign material, will not interfere with the quick and easy removal and replacement thereof.

Further objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings- Fig. 1 is a perspective view of a hammer mill constructed in accordance with the invention;

Fig. 2 is a side elevational view of the hammer mill shown in Fig. l; I

Fig. 3 is an end elevational view of the mill looking from right to left in Fig. 2;

Fig. 4 is a partial elevational view of one end of the main mill housing on approximately the line 44 of Fig. 2;

Fig. 5 is a detail view in end elevation illustrating the cage which supports the individual screens outside the main housing;

Figs. 6 and 7 are fragmentary views in plan and end elevation, respectively, showing the indexing mechanism for the cage;

Fig. 8 is a detail view in vertical section showing one of the individual screens for the hammer mill of Figs. 1-4;

Fig. 9 is a side view, partly broken away, illustrating the cooperative relation of one of the screens and the supporting portions of the cage;

Fig. 10 is a fragmentary top view looking downward on a portion of Fig. 9;

Fig. 11 is an enlarged view showing a fragment of Fig. 9 and looking from right to left in Fig. 9; and

Fig. 12 is a section on the line 1212 of Fig. 11.

The drawings illustrate a preferred embodiment of the invention in which the main housing of the hammer mill is constructed to receive and support a semi-cylindrical screen below the rotating hammers and thus directly between the hammers and the discharge outlet from the housing. A plurality of such screens, each of which may be of different mesh, are carried by a rotating cage on a stand located at one end of the housing, with the cage being rotatable in such relation with the housing as to bring any selected one of the screens into line with the position itis intended to occupy within the housing.

The housing is accordingly formed with an enlarged slot in its end wall facing the cage through which the selected screen may be inserted into operative position, and the stand carries a drive which is engageable with the selected screen to advance it into the housing and subsequently to retract it from the housing after use. This operation is facilitated by forming the slot of sufiiciently greater width than the working portion of the screen to permit easy insertion and removal of the screen, and the screen in turn is formed at its outer end with a flange or like widened portion which serves as a closure for the slot when the screen is fully advanced into operative position.

Referring more specifically to the drawings, the main housing It) includes an inlet hopper 11 at its upper end for the material to be ground, and the ground product is withdrawn from the lower end of the housing through an outlet 12 leading to the intake of a blower 13 which is shown as having its outlet 14 connected to an upwardly extending pipe 15 for transmission of the ground material to the desired bagger or other collecting station. The main drive motor 16 drives the blower and also the hammer shaft 17 which supports the rotating hammers within the main housing, and since these hammers may be of conventional design they are merely indicated diagrammatically at 18 in Fig. 2. p

The construction of one of the individual screens 20 is shown most clearly on Figs. 2 and 8. The semi-cylindrical perforated screen plate 21 is mounted in a cradle comprising a pair of main bars 22, front and back end flanges 23 and 25 respectively and a middle flange 26. The back flange 25 includes a semi-cylindrical forwardly projecting flange 27 which fits under the adjacent end of the screen plate, and the cradle also includes a pair of reinforcing bars 28 welded to the flanges 23, 25 and 26 outside the screen plate. In addition, a bar 30 is welded across the back end flange 25 to serve as a handle for manipulation of the screen.

The bars 22 of the screen cradle are of generally rectangular section, but each has an inwardly extending groove 33 along its outer side. These grooved portions of the bars 22 cooperate with complementary supports within the housing 10, and these supports are shown as a pair of angles 35 mounted within the housing. Also, the end wall 36 of housing 16 at the opposite end of the housing from the blower and drive motor is formed with an arcuate slot 45? proportioned to receive the screen therethrough, and the angles 35 extend outwardly of the housing for several inches through this slot.

The slot 4t? is specially proportioned with relation to the screen 23 to provide for easy insertion and removal of the screen through the slot while at the same time assuring complete closing of the slot when the screen is in fully operative position. Thus the radial dimension of the slot is sufliciently large to receive the cradle flanges 23 and 26 readily therethrough, but this dimension of the slot is sufliciently less than the corresponding dimension of the cradle flange 25 to cause flange 25 to overlap the slot in the fully inserted position of the screen and thus to serve as a closure for the slot. For example, satisfactory results have been obtained with the radial dimension of slot 49 equal to approximately 1.625 inch of the flange 25 has a corresponding dimension of 2.5 inches while the corresponding dimension of the screen measured across each of flanges 23 and 26 is 1.25 inches.

In order to provide for ready changing of the screens 20, a plurality of these screens is supported by a rotating cage 44 on a stand 45 mounted adjacent the slotted end wall of housing It Preferably these screens 20 are each of different mesh but of otherwise identical construction, as indicated by designating them 20a, 20b and 26c, respectively as in Figs. 1-3. The cage is constructed to support the three screens in angularly spaced relation with each other, and it is mounted on a shaft 46 for rotation by a drive indicated generally at 47 to locate a selected one of the screens in line with slot and angles 35 for insertion into the housing.

The cage 44 and its operative relation with each screen is best seen in Figs. 6-10. The cage comprises a pair of axially spaced spiders 50 each including three radially projecting portions 51, and these projections are connected in pairs by members 52 of modified channel shape. The spider 50 nearest stand has three flanges 53 projecting radially therefrom between the portions 51, and each of these flanges has a slot 54 in its outer end. This spider also carries a ring 55 mounted thereon by three welded bosses or studs 56, and ring 55 carries three grooved latch plates 57 on its outer surface, each in radial line with one of the projections 51. The plates 57 cooperate with a roller 60 carried by a lever 61 to latch the cage in indexed relation with the main housing, lever 61 being pivoted at 62 on stand 45 and being provided with a biasing spring 63.

The members 52 include side flanges 65 proportioned to fit within the grooved portions 33 of the screen bars 22 to form supporting tracks for the screen, and gibs 66 cooperate with the sides of bars 22 to guide the sliding movement of the screens on flanges 65. As shown in Fig. 5, each flange 65 extends at an angle of substantially 120 with respect to the adjacent main portion of the member 52 so that when the cage is positioned with one of its members 52 uppermost, the lowermost pair of flanges 65 will be substantially horizontal. Also, these parts are so proportioned that in this position of the cage, this lowermost pair of flanges 65 will be substantially directly in line with the angles 35 so that a screen 20 can be advanced along the cage and onto the angles for insertion into the housing. This operation is illustrated in Figs. 2, 9 and 10, and it will be noted that the outer end of each angle 35 is provided with a tapered upper surface 67 and a rounded outer end corner 63 to facilitate this movement of the screen.

The cage 44 and each screen 20 are also provided with cooperating parts for releasably locking the screens in retracted position on the cage. Each of the projections 51 on the spider 50 nearest stand 45 carries a pair of blocks 70 each having a spring loaded plunger 71 mounted therein for movement at substantially right angles to the adjacent flange 65, with these blocks 70 being mounted on opposite sides of the projection 51 to avoid interference with each other. Each of the bars 22 is formed in its upper surface with a recess 72 for receiving one of plungers 71, and each end of bar 22 is also beveled at 73 to form a cam facilitating insertion of this screen under the plungers 71.

The stand 45 also carries drive means for advancing and retracting the lowermost screen on cage 44 into and out of the housing 10. This drive includes a lead screw 75 supported by the stand and a bracket 76 and driven by a reversible drive indicated generally by the sprocket 77. The inner end of screw 75 carries a hook 38 which is so formed that when the cage rotates on shaft 46, the handle 3%) on the lowermost screen 2t) will automatically be carried into engaging position with this hook. Thus when the screw is driven in the direction to move from ri ht to left in Fig. 2, it will push the lowermost screen into the housing 10, and when it is driven in the opposite direction, it will retract this screen back onto the cage. It will also be noted that the screw 75 is arranged to pass through the slot 54 in the lowermost flange 53 on the cage, thus positively locking the cage against rotation until the screen has been withdrawn from the housing.

With this construction and arrangement, the cage 44 can carry a plurality of screens of different selected meshes, and the cage can be rotated into the proper indexed position with respect to slot 40 in the housing to locate the screen having the desired mesh in alignment with the slot. When it is desired to change the fineness of grinding, the screen 20 being used is pulled out of the housing by screw 75, the cage is rotated to locate a screen of the next desired mesh in indexed position, and since this rotation of the cage carries the previous screen out of engagement with hook and engages this hook with the indexed screen, the latter is then ready to be pushed into the housing. Not only can this screen changing be effected without stopping or even slowing down the operation of the mill, but during one grinding operation, one or both of the screens not being used can be changed on the cage.

In addition to the ease and speed of screen changing afforded by the present invention, it should be noted that these advantages are provided without undesirably increasing the overall dimensions of the mill as a whole and thus without requiring excessive floor space. In fact, the total amount of floor space needed by the cage and its support is not appreciably more than would be necessary in any event if the screens were manually mounted or removed from the mill. Furthermore, the present invention is adapted for remote control operation if desired. Thus the drivers or controls for the drives 47 and 77 can be located remotely from the mill, and the entire screen changing operation can be effected by such remote conrol. Still another advantage of the invention is that with the screen and mill housing constructed as disclosed, changing of the screen is not affected by puncture or like injury to a screen, since the closure flange on the screen makes it possible to utilize a slot and a housing of such width as to permit ready removal of even a damaged 7 screen without interference with any of the other operating parts.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a main housing having rotating hammers therein, a screen separate from said housing, means in said housing for supporting said screen in operative relation with said hammers, means in a vertical outer wall of said housing forming a slot proportioned to receive said screen therethrough and aligned with said supporting means to pro vide for insertion of the front end of said screen therethrough into supported relation with said supporting means, said slot being substantially wider than the thickness of said screen to facilitate insertion of said screen and especially to provide for ready removal of said screen in the event of damage thereto by a foreign body in the material being treated in said mill, and a flange on the rearward end of said screen of greater Width than said slot to form a closure for said slot in the fully inserted position of said screen.

2. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a. main housing having rotating hammers therein, a cylindrically curved screen, means in said housing for supporting said screen in operative relation below said hammers, means in an end wall of said housing forming an arcuate slot aligned with said supporting means and proportioned to receive the front end of said screen therethrough into supported relation with. said supporting means, said slot being substantially wider than the thickness of said screen to facilitate insertion of said screen and especially to provide for ready removal of said screen in the event of damage thereto by a foreign body in the material being treated in said mill, and a flange on the rearward end of said screen of greater width than said slot to form a closure for said slot in the fully inserted position of said screen.

3. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of individually separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer Wall of said housing forming an opening aligned with said supporting means and proportioned to provide for insertion of the front end of one of said screens therethrough into supported relation with said supporting means, a stand mounted in predetermined relation with and outside of said housing and including means for carrying said plurality of screens in separated relation to provide for insertion of a selected said screen therefrom in said housing while retaining the others of said screens outside said housing independently of said inserted screen, and means for shifting said carrying means with respect to said housing in a direction substantially transverse of the direction of insertion of said screens to locate a selected said screen thereon in aligned relation with said opening and said supporting mean-s for insertion through said opening onto said supporting means.

4. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of individually separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer wall of said housing forming an opening aligned with said supporting means and proportioned to provide for insertion of the front end of one of said screens therethrough into supported relation with said supporting means, a stand mounted in predetermined relation with and outside of said housing and including means for carrying said plurality of screens in separated relation to provide for insertion of a selected said screen therefrom in said housing while retaining the others of said screens outside said housing independently of said inserted screen, means for shifting said carrying means with respect to said housing in a direction substantially transverse of the direction of insertion of said screens to locate a selected said screen thereon in aligned relation with said opening and said supporting means for insertion through said opening onto said supporting means, and each said screen including a flange portion of greater width than said opening to form a closure for said opening in the fully inserted position of said screen.

5. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of individually separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer wall of said housing forming an opening aligned with said supporting means and proportioned to provide for insertion of the front end of one of said screens therethrough into supported relation with said supporting means, a stand mounted in predetermined relation with and outside of said housing and including a plurality of tracks supporting said plurality of screens in spaced relation, means for shifting said tracks on said stand transversely of the direction of insertion of said screens to locate a selected said screen and the tracks therefor in aligned relation with said opening and said supporting means, and drive means for advancing said selected screen along said tracks and through said opening into supported relation with said supporting means, said drive means being reversible to retract said selected screen from said housing to provide for replacement thereof by another of said screens following further said shifting movement of said tracks.

6. A hammer mill adapted for quick changing of the screen Without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer wall of said housing forming an opening aligned with said supporting means and proportioned to provide for insertion of one of said screens therethrough into supported relation with said supporting means, a stand mounted outside of said housing and including a cage for carrying said plurality of screens in angularly spaced relation, means for rotating said cage with respect to said housing to locate a selected said screen thereon in aligned relation with said opening for insertion through said opening onto said supporting means, and reversible drive means on said stand engageable with said selected screen for moving said screen through said opening onto and back from said supporting means in said housing.

7. A hammer mill adapted for quick changing of the screen Without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of separate screens, means in said housing for supporting a selected one of said screens in operative relation with. said hammers, means in a vertical outer wall of said housing forming an opening aligned Wiht said supporting means and proportioned to provide for insertion of one of said screens therethrough into supported relation with said supporting means, a stand mounted outside of said housing and including a cage for carrying said plurality of screens in angularly spaced relation,

means for rotating said cage with respect to said housing to locate a selected said screen thereon in aligned relation with said opening for insertion through said opening onto said supporting means, reversible drive means on said stand engageable with said selected screen for moving said screen through said opening onto and back from said supporting means in said housing, and cooperating interlocking means on said cage and said drive means for preventing rotation of said cage except when said selected screen is fully retracted from said housing and onto said cage.

8. A hammer mill adapted for quick changing of the screen Without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer wall of said housing forming an opening aligned With said supporting means and proportioned to provide for insertion of one of said screens therethrough into supported relation with said supporting means, a stand mounted in predetermined relation with and outside of said housing and including means for carrying said plurality of screens in spaced relation, means for shifting said carrying means with respect to said housing to locate a selected said screen thereon in aligned relation with said opening and said supporting means for insertion through said opening onto said supporting means, means on said carrying means for releasably retaining the others of said screens thereon, and said retaining means being constructed and arranged to provide for release and removal of said other screens at either end or" said carrying means Without affecting operation of said selected screen in. said housing.

9. A hammer mill adapted for quick changing of the screen without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer wall of said housing forming an opening aligned with said supporting means and proportioned to provide for insertion of one of said screens therethrough into supported relation with said supporting means, a stand mounted outside of said housing and including a cage supported thereon for rotation with respect to said housing, means on said cage forming a plurality of tracks for carrying said plurality of screens in angularly spaced relation, means for rotating said cage to locate a selected said screen thereon with said tracks therefor aligned with said supporting means, and reversible drive means on said stand engageable with said selected screen for moving said screen along said tracks through said opening and onto said supporting means and for thereafter retracting said screen back onto said tracks.

10. A hammer mill adapted for quick changing of the screen Without interruption of operation, comprising a main housing having rotating hammers therein, a plurality of separate screens, means in said housing for supporting a selected one of said screens in operative relation with said hammers, means in a vertical outer Wall of said housing forming an opening aligned With said supporting means and proportioned to provide for insertion of one of said screens therethrough into supported relation with said supporting means, a stand mounted outside of said housing and including a cage supported thereon for rotation With respect to said housing, means on said cage forming a plurality of tracks for carrying said plurality of screens in angularly spaced relation, yieldable means normally retaining all of said screens on said cage in retracted position with respect to said housing, means for rotating said cage to locate a selected said screen thereon With said tracks therefor aligned with said supporting means, reversible drive means on said stand engageable with said selected screen for moving said screen along said tracks through said opening and onto said supporting means and for thereafter retracting said screen back onto said tracks, and said retaining means being releasable upon movement of the associated said screen in either direction from said retracted position thereof to provide for release and removal of said other screens at either end of said cage rithout affecting said selected screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,227,090 Hughes Dec. 31, 1940 2,360,892 Rench Oct. 24, 1944 2,488,714 Delp Nov. 22, 1949 

